Originally Posted by ww2birds

Hi CTU fans. I just spent a few hours on the test stand with a Merlin 200XBL turbine (with the brushless/digital pump) connected to the CTU.

My goal was to find the correct fuel consumption calibration number (Pump Factor), which for this setup I estimate to be 46.

Details:

I had flown the CTU (and really like it!) and found the suggested pump factor of 200 to be reporting waaaay to little fuel consumption. With Gapsar's "Telemetry 1" adapter or his Flight Computer, he suggests a default of 200. Just as Sandor does. With the Xicoy Tele-1 and FC devices hooked to the 200XBL I found that the more correct number was 185-187 .. so the 200 setting was conservative .. so that is sensible.

Clearly something very different is going on with the CTU's calculation (which is just fine .. they never stated compatible fuel factors with the Gaspar units).

After several calibration runs (as outlined in the CTU's manual) I'd say that the correct pump factor for this motor on the CTU is approximately 46 (perhaps +/-2) .. it repeated on two calibration runs and reports not only the 1L "measured mile" correctly as in the manual, but it also gets the total fuel consumption within a few percent from before startup to after shutdown when compared to the weight change of the fuel tank. I used Sandor's 0.8Kg/L fuel density number.

I was using a BVM UAT, all 1/8" (3.2mm) ID tygon on the inlet side, the usual 4mm clear tubuing on the pump output, and a 3S LiFE ECU battery.

I would be curious if others have also determined similar factors. Perhaps it is very different for the old DC motors and the brushless digital pump?

Dave